Wire cut electric discharge machine

ABSTRACT

A wire cut electric discharge machine provided with a machining fluid supply apparatus capable of supplying machining fluid in an amount large enough to permit a stable wire extension even in a finishing operation. During rough machining, a first flow regulating valve (6) provided in a first pipe (3) and a second flow regulating valve (10) and an on-off valve (11) respectively provided in a second pipe (4) are fully opened, so that machining fluid is injected from upper and lower nozzles (5, 9) respectively connected to these pipes. In the finishing operation, openings of the first and second flow regulating valves are reduced. When wire extension is carried out, the on-off valve in the second pipe is fully closed, and an on-off valve (7) provided in a bypass pipe (8) and fully closed during both the rough machining and the finishing operation is fully opened, whereby an amount of machining fluid large enough to reliably guide a wire electrode is injected from a jet nozzle connected to the bypass pipe and attached to the upper nozzle, regardless of the opening of the first flow regulating valve which varies between the rough machining and the finishing operation.

TECHNICAL FIELD

The present invention relates to a wire cut electric discharge machine,and more particularly, to a machining fluid supply apparatus capable ofsupplying machining fluid in an amount enough to ensure stable wireextension even in a finishing operation.

BACKGROUND ART

Generally, a wire cut electric discharge machine comprises upper andlower nozzles respectively provided at upper and lower wire guides, andmachining fluid supply pipe lines connected to these nozzles, and isarranged to inject machining liquid from the upper and lower nozzlestoward an electric discharge machining region between a workpiece and awire electrode, to thereby remove the sludge and heat produced duringelectric discharge machining. For rough machining, the opening degreesof flow regulating valves respectively provided in the machining fluidsupply pipe lines are increased, to thereby supply the machining fluidin an amount large enough to remove the sludge and heat that areproduced in large quantities during the rough machining. On the otherhand, in a finishing operation including a second cut, the valveopenings are decreased, so as to reduce a deviation of the wireelectrode due to the injection pressure of the machining fluid, tothereby improve machining accuracy.

In the aforementioned type of electric discharge machine, it is known tocarry out automatic wire extension by using the machining fluid. Namely,at the time of wire extension, the machining fluid is jetted toward theworkpiece from a jet nozzle mounted to the upper nozzle, while theinjection of the machining fluid from the lower nozzle is interrupted.Then, the wire electrode is fed from the upper wire guide, while beingrestricted by the jet of the machining fluid, so that the wire passesthrough a machining initial hole formed in the workpiece and the wirepassage of the lower wire guide, thereby effecting the wire extension.

During a finishing operation, however, since the openings of the flowregulating valves in the machining fluid supply pipe lines are small,the amount of the machining fluid supplied to the jet nozzle is reduced,and hence the injection pressure of the jet stream of machining fluid islowered. The thus reduced injection pressure sometimes causes anunsuccessful wire extension performed in the middle of a finishingoperation.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a wire cut electricdischarge machine equipped with a machining fluid supply apparatuscapable of supplying machining fluid in an amount large enough to ensurestable wire extension even in a finishing operation.

To achieve the above-mentioned object, a wire cut electric dischargemachine of the present invention comprises a main pipe line connecting amachining fluid supply source to an upper nozzle, a bypass pipe lineconnecting the machining fluid supply source to the upper nozzle, a flowregulating valve provided in the bypass pipe line, and control means forvarying an opening of the flow regulating valve in dependence on whetheror not the electric discharge machine is operated in a wire extensionmode.

As described above, according to the present invention, the opening ofthe flow regulating valve disposed in the bypass pipe line, which isprovided separately from the main pipe line, is varied in dependence onwhether or not the electric discharge machine is operated in the wireextension mode. Accordingly, it is possible to supply an amount ofmachining fluid large enough to permit stable wire extension even in afinishing operation, whereby the wire extension can be reliablyperformed.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE is a schematic diagram showing a principal part of awire cut electric discharge machine according to an embodiment of thepresent invention.

BEST MODE OF CARRYING OUT THE INVENTION

Referring to the appended drawing, a wire cut electric discharge machineof an embodiment of the present invention comprises a tank 1 for storingmachining fluid, a pump 2 for pressurizing the machining fluid suppliedfrom the tank 1, and a motor 12 for driving the pump 2. First and secondpipe lines 3 and 4 are connected at their one ends to the discharge portof the pump 2. Other ends of these pipe lines 3, 4 are respectivelyconnected to upper and lower nozzles 5 and 9. First and second automaticflow regulating valves 6 and 10 are disposed in the middle of the firstand second pipe lines 3, 4, respectively. Preferably, these valves 6, 10are each provided with a flow meter, not shown. One end of a bypass pipeline 8 is connected to that portion of the first pipe line (main pipeline) 3 which is located upstream of the first flow regulating valve 6,and the other end of the bypass pipe line 8 is connected to a portion ofthe first pipe line 3 downstream of the valve 6. Further, a third flowregulating valve 7, which preferably consists of an electromagneticvalve, is disposed in the middled of the bypass pipe line 8, and afourth flow regulating valve 11, which also preferably comprises anelectromagnetic valve, is arranged in a portion of the second pipe line4 upstream of the valve 10. Electromagnetic valve actuators 14 and 15,respectively associated with the valves 7 and 11, and the motor 12 areconnected to a numerical control unit 13 containing a computer forcontrolling the operation of the electric discharge machine.

The operation of the electric discharge machine will now be described.

During rough machining, the first and second automatic flow regulatingvalves 6, 10 are fully opened under the control of the numerical controlunit 13, and the electromagnetic valve 7 is fully closed while theelectromagnetic valve 11 is fully opened, respectively by theelectromagnetic valve actuators 14, 15 which respond to control outputsfrom the numerical control unit 13. Further, the motor 12 is drivenunder the control of the numerical control unit 13. As a result, themachining fluid from the tank 1 is pressurized by the pump 2 driven bythe motor 12, and is supplied to the upper and lower nozzles 5, 9 viathe first and second pipe lines 3, 4. Since the valves 6, 10 and 11 arefully opened, a sufficient amount of machining fluid is supplieduniformly from the upper and lower nozzles 5, 9 toward an electricdischarge machining region (not shown). Thus, the sludge and heat, whichare produced in a relatively large quantity during the rough machiningin which machining is effected with relatively large discharging energyat a high speed, can be smoothly removed, whereby the electricdischarging at the electric discharge machining region can be stablycontinued. During the rough machining, the electromagnetic valve 7 isfully closed as mentioned above, and therefore, the supply of machiningfluid via the bypass pipe line 8 is interrupted.

During a second cut and subsequent finishing process, the motor 12 iscontinuously driven under the control of the numerical control unit 13,and the electromagnetic valves 7, 11 are maintained in the fully closedstate and fully open state, respectively. Accordingly, the supply of themachining fluid from the pump 2 to the first and second pipe lines 3 and4 is continued, while the supply of the machining fluid via the bypasspipe line 8 is still stopped. On the other hand, the openings of thefirst and second flow regulating valves 6, 10 are reduced to presetopenings under the control of the numerical control unit 13.Accordingly, the amount of machining fluid injected from the upper andlower nozzles 5, 9 toward the electric discharge machining region isdecreased, and thus the injection pressure of the machining fluid isreduced to such a value that a wire electrode (not shown) is notdeviated even in the finishing operation where the machining is effectedwith low discharging energy at a low speed by the use of a relativelythin wire electrode. Meanwhile, the aforesaid preset openings of thevalves 6, 10 are set such that the machining fluid is supplied in anamount large enough to remove the sludge and heat produced during thefinishing operation.

Upon reading a wire extension command from a program, the numericalcontrol unit 13 drives a conventional driving mechanism (not shown), toattach a jet nozzle (not shown) to the upper nozzle 5, and then drivesthe electromagnetic valve actuators 14, 15 to thereby fully open theelectromagnetic valve 7 and fully close the electromagnetic valve 11,respectively. Then, the numerical control unit 13 drives the pump 2 viathe motor 12, and starts feeding the wire electrode through the upperwire guide (not shown). Since the electromagnetic valve 7 is fullyopened, the machining fluid from the pump 2 is jetted toward theworkpiece from the jet nozzle via the bypass pipe line 8 and the uppernozzle 5. On the other hand, the electromagnetic valve 11 is fullyclosed, and hence, the supply of machining fluid via the lower nozzle 9is interrupted.

The wire electrode is fed toward the workpiece while being restricted bythe jet of machining fluid. Since the electromagnetic valve 7 is fullyopened as described above, a sufficient amount of machining fluid issupplied through the bypass pipe line 8, without influence by theopening of the flow regulating valve 6. Therefore, even when the wireextension is started in the middle of a finishing operation in which theopening of the flow regulating valve 6 is kept small, a sufficientlyhigh pressure of the machining fluid jet is insured. Accordingly, thewire electrode can be reliably guided by a required jet pressure, andsmoothly inserted into the machining initial hole of the workpiece andthen into a wire passage (not shown) of the lower wire guide.

Thereafter, after the wire electrode is introduced to a wire conveyingdevice (not shown) provided on the downstream side of the lower wireguide so that the wire extension is completed, a detection signalindicating the completion of wire extension is supplied to the numericalcontrol unit 13 again brings the electromagnetic valve 7 into a fullyclosed state and the electromagnetic valve 11 into a fully open state.The jet nozzle is then detached from the upper nozzle 5, and is resetinto a retracted position.

The present invention is not limited to the above embodiment, andvarious modification thereof may be made. For example, in theembodiment, an automatic flow regulating valve is used for the first andsecond valve may be used. Moreover, during the wire extension, the firstflow regulating valve 6 may be fully closed.

We claim:
 1. A wire cut electric discharge machine comprising:a mainpipe line connecting a machining fluid supply source and an uppernozzle; a bypass pipe line connecting the machining fluid supply sourceand the upper nozzle; a flow regulating valve provided in said bypasspipe line; and control means for varying an opening of said flowregulating valve in dependence on whether or not the electric dischargemachine is operated in a wire extension mode, the opening controlled tobe larger in the wire extension mode than in a mode which is not thewire extension mode, so that a sufficient amount of machining fluid issupplied to permit wire extension during a finishing operation.
 2. Awire cut electric discharge machine according to claim 1, wherein saidflow regulating valve comprises an on-off valve, and said control meansfully opens said on-off valve when the electric discharge machine isoperated in the wire extension mode, and fully closes said on-off valvewhen the electric discharge machine is not operated in the wireextension mode.
 3. A wire cut electric discharge machine according toclaim 2, wherein said control means fully opens said on-off valve whensupply of machining fluid for wire extension is started, and fullycloses the on-off valve when said supply of machining fluid is ended. 4.A wire cut electric discharge machine according to claim 1, furtherincluding:a flow regulating valve provided in said main pipe line;wherein said electric discharge machine is arranged to vary an amount ofmachining fluid supplied through said main pipe line between when saidmachine is operated in a rough machining mode and when said machine isoperated in a finishing mode; and wherein said control means varies theopening of said flow regulating valve provided in said bypass pipe linesuch that a required amount of machining fluid is supplied through saidbypass pipe line, regardless of an opening of said flow regulating valveprovided in said main pipe line.
 5. A wire cut electric dischargemachine according to claim 4, further including:a second main pipe lineconnecting said machining fluid supply source and a lower nozzle; and aflow regulating valve and an on-off valve respectively provided in saidsecond main pipe line; wherein said electric discharge machine isarranged to vary an amount of machining fluid supplied through saidsecond main pipe line between when said machine is operated in the roughmachining mode and when the said machine is operated in the finishingmode; and wherein said control means fully closes said on-off valveprovided in said second main pipe line when said electric dischargemachine is operated in the wire extension mode.